Integrated noise cancellation and residual echo suppression

ABSTRACT

A combined processor, such as might be used in a mobile handset or hands-free communication device, provides residual echo suppression and noise reduction while eliminating the need for explicit comfort noise generation. Operating within a near-end communication device, the processor receives an echo-canceled signal that is derived from a near-end input signal, and generates an output signal for subsequent transmission to a far-end communication device by applying a noise attenuation factor to the echo-canceled signal or to an average of that signal. The processor maintains the average signal across periods of speech and non-speech. During far-end-modes of operation, where only incoming audio from the far-end is active, the processor substitutes the average signal for the echo-canceled signal, such that a far-end listener receives the natural sounding average signal without receiving the objectionable, residual echo that may be in the echo-canceled signal.

BACKGROUND OF THE INVENTION

[0001] The present invention generally relates to a method and apparatusfor echo suppression and noise cancellation in a communications device,and more particularly to integrated noise cancellation and residual echosuppression in a wireless communications device.

[0002] Near-end background noise and far-end echo are frequently presentduring communications between a far-end user and a near-end user. Mostcommunications devices utilize noise and echo suppression techniques.Without such techniques, the far-end user receives a signal muddled bybackground noise and echo signals.

[0003] Echo processing is well known in the art. Generally, an echoprocessor operates in one of four speech modes: near-end mode (near-endspeech only), far-end mode (far-end speech only), double-talk mode(near- and far-end speech), and quiet mode (no speech). Conventionalecho processors include front-end echo cancellation as well as residualecho suppression and noise reduction capabilities. Many communicationdevices prone to echo problems use linear echo cancellers (LEC) toimplement front-end echo cancellation. The resulting echo-canceledsignal typically includes residual echo and near-end background noise.

[0004] Generally, a residual echo suppressor attenuates theecho-canceled signal to reduce the background noise and the residualecho. The amount of attenuation is dependent on the current speech mode.For example, in far-end mode, the residual echo suppressor increases theattenuation to effectively block the near-end input signal. Thistechnique effectively suppresses background noise and residual echo, butthe resulting echo- and noise-free signal received by the far-end useris unnaturally quiet. The sudden loss of background noise often makesthe far-end user uncomfortable. Further, the unnatural silence may causethe far-end user to believe that the connection has been lost. Tocompensate, the echo processor at the near-end generates comfort noisefor transmission to the far-end user during far-end mode.

[0005] While conventional echo suppression and noise reductiontechniques effectively suppress or eliminate echo and background noise,these techniques also cause abrupt changes in received background noiselevels. Further, because such techniques effectively block the near-endsignal during some modes of operation, explicit comfort noise generationis required.

SUMMARY OF THE INVENTION

[0006] The present invention comprises a method and apparatus forcombining residual echo suppression (RES) and noise reduction (NR)within a communication device, thereby eliminating the need for explicitcomfort noise generation. Such need is eliminated by deriving an outputsignal for transmission by the near-end device from the echo-canceled(EC) signal, or from an average of the echo-canceled signal thereof,depending on a current mode of operation. During a far-end mode ofoperation, where there is only received audio from the far end, theoutput signal is generated by applying a first attenuation factor to theaverage echo-canceled signal, herein referred to as the average signal.The first attenuation factor is a function of an average noise. Theaverage noise comprises an average of an estimated noise of theecho-canceled signal. Applying the first attenuation factor to theaverage signal avoids the need for comfort noise generation, while stillpreventing the return of objectionable echo to the far end.

[0007] In an exemplary embodiment, a combined processor within thecommunication device maintains the estimated noise, the average noise,and the average signal across all modes of operation. Such modes ofoperation include a far-end mode, where only far-end speech is active, anear-end mode where only near-end audio input (e.g. speech) is active, adouble-talk mode where both far-end and near-end audio input are active,and a quiet mode, which may still include noise but where there is noactive audio input, such as speech. Generally, the modes may be thoughtof as quiet mode and non-quiet mode, where the non-quiet modeencompasses all of the various speech modes.

[0008] The combined processor generates the output signal by operatingon the EC signal responsive to a current operating mode. If the currentoperating mode is not the far-end mode, the processor generates theoutput signal by applying a second attenuation factor to the EC signalsuch that the far-end listener receives an echo-suppressed andnoise-attenuated version of the actual near-end input signal.

[0009] However, during far-end mode, the processor generates the outputsignal by substituting the average signal for the EC signal and bysubstituting the first attenuation factor for the second attenuationfactor. That is, the processor generates the output signal by applyingthe first attenuation factor to the average signal, thus avoiding thereturn of residual echo, which is particularly problematic in far-endmodes, while still providing a natural sounding surrogate for the ECsignal.

[0010] In one or more exemplary embodiments, the combined processorcomprises a background noise estimator, an average signal generator, anoutput signal generator, and activity decision logic (mode controllogic). The background noise estimator maintains the estimated noise by,in an exemplary embodiment, tracking a power spectral density (PSD) ofthe EC signal for quiet modes and for a combination of quiet andnon-quiet modes. Further, the background noise estimator generates anaverage of the PSD during quiet and non-quiet modes. These PSD valuesdetermine the amount of attenuation applied by the output signalgenerator.

[0011] As with the background noise estimator, the average signalgenerator is active across all modes of operation, and maintains, in anexemplary embodiment, the average signal as a running average of thespectral magnitudes of the EC signal. As noted, it carries thisaveraging across quiet and non-quiet modes of operation such that theaverage signal provides a natural sounding surrogate for the EC signalduring far-end mode operations. Note that the manner in which theaverage signal is maintained may be varied, but an exemplary approachuses an exponential weighting filter to develop the running average witha desired weighting bias between the older and newer signal values thatform the average. Such exponential weighting or other desired filteringmay also be applied to the PSD values maintained by the background noiseestimator.

[0012] Regardless, the output signal generator receives the noiseattenuation factors from the background noise estimator and receives theaverage signal from the average signal generator. Alternatively, theoutput signal generator may compute the first and second attenuationfactors based on receiving the PSD values from the background noiseestimator. Further, the output signal generator receives the EC signalfrom, for example, a front-end echo canceller that has removed at leastsome portion of the echoed far-end components from the near-end inputsignal. Thus, the output signal generator generates the output signalusing the average signal or the EC signal, with its selective use ofeither signal being responsive to one or more mode indicator signalsprovided to it by the activity decision logic.

[0013] In either case, the output signal typically is subjected toadditional processing by associated transceiver processing resources,and is formatted, processed or otherwise encoded for transmission to thefar-end device, such as by sending the suitably processed output signalvia wireless transmission to a supporting wireless network. Of course,as the present invention is readily adaptable to both wirelesscommunication devices and land-line communication devices, the detailsof the network(s) supporting communication between the near-end andfar-end devices may vary considerably.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 illustrates an exemplary communications system in which thepresent invention may be used.

[0015]FIG. 2 illustrates conventional echo cancellation in acommunications device.

[0016]FIG. 3 illustrates an exemplary communications device thatincludes echo processing according to one or more embodiments of thepresent invention.

[0017]FIG. 4 illustrates exemplary echo processing details for thedevice of FIG. 3.

[0018]FIG. 5 illustrates exemplary control logic circuitry for thedevice of FIG. 4.

[0019]FIG. 6 illustrates exemplary flow logic for exemplary residualecho suppression and noise cancellation according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0020]FIG. 1 illustrates an exemplary communications system 10 in whichthe echo suppression techniques of the present invention may beadvantageously used. The communications system 10 includes acommunications tower 22, base station 24, Mobile Switching Center 20(MSC), and a transmission network, such as the Public Switched TelephoneNetwork (PSTN) 26. A conventional near-end mobile terminal 40communicates with a far-end conventional telephone handset 30 viacommunications system 10. The mobile terminal 40 receives and encodes avoice input from microphone 42, and transmits the voice signal to theMSC 20 via tower 22 and associated base station 24. MSC 20 furtherprocesses and transmits the received signals to a far-end conventionaltelephone handset 30 via PSTN 26. The telephone handset 30 outputs afacsimile of the mobile terminal user's voice based on these receivedsignals.

[0021] Conversely, the telephone handset 30 conveys voice input from afar-end user to MSC 20 via PSTN 26. MSC 20 encodes and transmits thereceived far-end signal to mobile terminal 40 via base station 24 andtower 22. Mobile terminal 40 receives and decodes these transmittedsignals. After decoding, mobile terminal 40 outputs a facsimile of thefar-end user's voice at loudspeaker 44.

[0022] Voice signals from the far-end user, as reproduced by loudspeaker44 in mobile terminal 40, undesirably couple into microphone 42 ofmobile terminal 40, creating a far-end echo. Thus, the far-end userreceives signals representative of the mobile terminal user's voice(near-end voice) and near-end background noise, as well as an echosignal representative of his or her own transmitted voice (echoedfar-end voice). As newer mobile terminals 40 become increasinglysmaller, the diminished physical separation of the included loudspeaker44 and microphone 42 increases these acoustic coupling problems.

[0023]FIG. 2 illustrates the conventional echo processing of mobileterminal 40, which includes microphone 42, loudspeaker 44, echoprocessor 50, and transceiver 60. Transceiver 60 processes near-endsignals for transmission and received far-end signals, according toconventional methods. Transceiver 60 typically includesanalog-to-digital circuitry (ADC), a transmitter digital signalprocessor (DSP), a modulator/RF amplifier, a receiver/amplifier, areceiver DSP, and digital-to-analog circuitry (DAC), not shown. Thetransmitter DSP (not shown) typically includes a speech coder andchannel coder (not shown) to process the digitized near-end input signalprepare it for transmission in accordance with requirements of thecommunications system 10. The receiver DSP receives and processes thedown-converted received signals in accordance with the requirements ofthe communications system 10, and produces output signal d(t).Loudspeaker 44 converts the digitized far-end signal d(t) produced bytransceiver 60 into an audible signal representative of sounds (voiceand noise) from the far-end communications device.

[0024] Mobile terminal 40 receives near-end acoustic signals atmicrophone 42 and converts these acoustic signals to a near-end inputsignal u(t). The near-end input signal u(t) includes signal componentsrepresentative of the mobile terminal user's voice (desired voice), thenear-end background noise (ambient noise), and/or far-end echo resultingfrom the audible signal from loudspeaker 44 coupling to microphone 42.

[0025] Echo processor 50 includes an echo canceller (EC) 52, whichtypically includes a linear echo canceller (LEC), summing junction 54,residual echo suppressor (RES) 56, and comfort noise generator 58. EC 52functions as an adaptive filter to produce an estimate of the far-endecho signal, called the estimated-echo signal {circumflex over (d)}(t),based on processing the near-end output signal d(t) generated bytransceiver 60. Summing circuit 54 combines the near-end input signalu(t) with the estimated-echo signal {circumflex over (d)}(t), andoutputs an echo-canceled signal x(t). The main elements of theecho-canceled signal x(t) may be categorized as desired voice,background noise, and residual echo.

[0026] RES 56 receives echo-canceled signal x(t) and attenuates signalx(t), under the direction of a control signal provided by EC 52, toproduce a residual echo suppressed signal z(t). Comfort noise generator58 then adds comfort noise to residual echo suppressed signal z(t). Theamount of comfort noise added by comfort noise generator 58 may dependon the attenuation of RES 56. For example, during far-end modeoperations, z(t)→0 because RES 56 effectively blocks echo-canceledsignal x(t), while during the remaining speech modes, z(t) may be nearlyequivalent to x(t). Therefore, during far-end mode, comfort noisegenerator 58 adds comfort noise to signal z(t); during near-end, quiet,and double-talk modes, comfort noise generator 58 simply passes signalz(t).

[0027]FIG. 3 illustrates a mobile terminal 100 according to the presentinvention. Mobile terminal 100 may be used in a conventional network,such as the network shown in FIG. 1. While FIG. 1 depicts a mobileterminal 40, such illustration is for benefit of understanding thediscussion herein and should not be construed as limiting theapplication of the present invention. Echo suppression, as practiced inaccordance with exemplary embodiments of the present invention, mayinvolve echo suppression in or between various types of communicationdevices. Examples of such devices include mobile telephones,speaker-phones, hands-free communications devices, and various othervoice or data systems. Thus, the present invention may be advantageouslyused to improve echo suppression in a broad range of communicationsdevices and networks.

[0028] Mobile terminal 100 includes microphone 110, keypad 112, display,114, and loudspeaker 120 for receiving and communicating signals andcontrols to and from mobile terminal 100. Mobile terminal 100 alsoincludes transmitter 150, receiver 152, antenna assembly 156, basebandprocessor 160, system control 190, ADC 192, and DAC 194. System control190 interfaces with baseband processor 160 and switch 154 to coordinatetransmission and reception operations. Keypad 112 interfaces with thesystem control 190 and allows the user to dial numbers, enter commands,and select various options. Display 114 interfaces with the systemcontrol 190 and enables the user to monitor call status and view otherservice information.

[0029] Mobile terminal 100 receives signals from a far-endcommunications device through antenna assembly 156. Switch 154, incooperation with antenna 156 and system control 190, switches receivedsignals from antenna 156 to receiver 152. Receiver 152 down-converts thereceived signals to a desired baseband frequency. Receiver 152 mayfurther amplify the down-converted signals to levels appropriate forsubsequent processing by the baseband processor 160. Baseband processor160 typically includes a transmitter/receiver (Tx/Rx) processor 162 andecho processor 170. Tx/Rx processor 162 processes the received signalsaccording to conventional methods and generates a processed far-endsignal d(t). Such processing may include equalization, demodulation, anddecoding. Echo processor 170 implements echo cancellation.

[0030] DAC 194 converts the processed far-end signal d(t) to an analogaudio signal. DAC 194 may include a digital-to-analog converter andother amplification and filtering circuitry, as necessary. Loudspeaker120 receives the analog audio signal from DAC 194 and converts theanalog audio signal into an analog signal representative of sounds(far-end voice and noise) from a far-end communications device (notshown). Microphone 110 detects and couples a portion of the soundsemanating from loudspeaker 120 with other near-end audio input signals.

[0031] ADC 192 generates a digitized near-end input signal u(t) of theaudio input signal from microphone 110. The near-end input signalincludes near-end speech, near-end background noise, and/or far-endecho. ADC 192 may include an analog-to-digital converter and otheramplification and filtering circuitry, as necessary. Baseband processor160 receives and processes the near-end input signal u(t) fortransmission. Tx/Rx processor 162 and transmitter 150 processes thedigitized near-end signal u(t) for transmission to a far-end user viaantenna 156. Such processing may include echo processing, coding (speechand channel), up-conversion, modulation, and amplification.

[0032]FIG. 4 further illustrates the details of echo processor 170. Echoprocessor 170 includes echo canceller 172, summing circuit 174, controllogic circuit 176, and combined processor 180. Echo canceller 172functions as an adaptive filter to produce an estimate of the far-endecho signal, {circumflex over (d)}(t), based on processing the near-endloudspeaker output signal d(t). Summing circuit 174 combines anestimated echo signal {circumflex over (d)}(t), generated by EC 172,with the near-end input signal u(t) to generate the echo-canceled (EC)signal x(t) for combined processor 180. Combined processor 180 generatesan output signal by operating on the EC signal responsive to a currentoperating mode. The control logic 176 detects the current operatingmode.

[0033] Combined processor 180 includes background noise estimator 182,output signal generator 184, and average signal generator 186. Combinedprocessor 180 generates an output signal, Y(ω), during all modes ofoperation. During far-end mode, Y(ω) is a function of an average of theecho-canceled signal and an average of the estimated noise, as shown inEquation 1a. In Equation 1a, {overscore (X)}(ω) represents the averagesignal and {overscore (N)}(ω) represents the average noise.

Y(ω)={overscore (X)}(ω)−{overscore (N)}(ω),  (Equation 1a)

[0034] During near-end, double-talk, and quiet modes, Y(ω) is a functionof the EC signal X(ω) and the estimated noise {circumflex over(N)}(ω)(see Equation 1b).

Y(ω)=X(ω)−{circumflex over (N)}(ω),  (Equation 1b)

[0035] The background noise estimator 182 generates a first noise ratio,α₁(ω), as a function of a power spectral density (PSD) of x(t) duringquiet (noise only) mode (Φ_(N)(ω)) and an average of the PSD of x(t)across all (speech and noise) modes ({overscore (Φ)}_(N+S)(ω)), seeEquation 2a. $\begin{matrix}{{{\alpha_{1}(\omega)} = \frac{\Phi_{N}(\omega)}{{\overset{\_}{\Phi}}_{N + S}(\omega)}},} & \left( {{Equation}\quad 2a} \right)\end{matrix}$

[0036] Further, the background noise estimator 182 generates a secondnoise ratio, α₂(ω), as a function of a power spectral density (PSD) ofx(t) during quiet mode (Φ_(N)(ω)) and a PSD of x(t) across all modes(Φ_(N+S)(ω)), see Equation 2b $\begin{matrix}{{{\alpha_{2}(\omega)} = \frac{\Phi_{N}(\omega)}{\Phi_{N + S}(\omega)}},} & \left( {{Equation}\quad 2b} \right)\end{matrix}$

[0037] Equation 3 represents one method for calculating the average PSDacross all modes, {overscore (Φ)}_(N+S)(ω), where λ_(Φ) represents anexponential weighting factor.

{overscore (Φ)}_(N+S)(ω)=λ_(Φ){overscore(Φ)}_(N+S)(ω)+(1−λ_(Φ))Φ_(N+S)(ω),  (Equation 3)

[0038] Different exponential weighting factors may be used duringdifferent modes of operation. For example, during quiet modesλ_(Φ)=λ_(N); during speech modes λ_(Φ)=λ_(S). Background noise estimator182 may also calculate a first attenuation factor, β1(ω), according toEquation 4a, and a second attenuation factor β₂(ω), according toEquation 4b.

β₁(ω)=1−α₁  (Equation 4a)

β₂(ω)=1−α₂  (Equation 4b)

[0039] Average signal generator 186 generates the average signal{overscore (X)}(ω). The average signal {overscore (X)}(ω) may be arunning average of the EC signal X(ω) during all modes, calculatedaccording to

{overscore (X)}(ω)=λ{overscore (X)}(ω)+(1−λ)|X(ω)|²,  (Equation 5)

[0040] where λ is an averaging constant.

[0041] Output signal generator 184 receives EC signal (X(ω)), theaverage signal ({overscore (X)}(ω)), and first and second noise ratios(α₁(ω), α₂(ω)). Output signal generator 184 may also receive first andsecond attenuation factors (β₁(ω), β₂(ω)). When an indicator fromcontrol logic 176 indicates that a far-end mode is active, combinedprocessor 170 generates the output signal Y(ω) as a function of theaverage signal {overscore (X)}(ω) and the average noise estimate{overscore (N)}(ω) according to Equation 6.

Y(ω)={overscore (X)}(ω)−{overscore (N)}(ω)={overscore(X)}(ω)·(1−α₁)={overscore (X)}(ω)·β₁(ω)  (Equation 6a)

{overscore (N)}(ω)={overscore (X)}(ω)·α₁  (Equation 6b)

[0042] When the indicator from control logic 176 indicates thatnear-end, double-talk, or quiet modes are active, combined processor 170generates the output signal Y(ω) as a function of the EC signal X(ω) andthe estimated noise {circumflex over (N)}(ω) as shown in Equation 7.

Y(ω)=X(ω)−{circumflex over (N)}(ω)=X(ω)·(1−α₂)=X(ω)·β₂(ω)  (Equation 7a)

{circumflex over (N)}(ω)=X(ω)·α₂  (Equation 7b)

[0043] The above equations are presented in frequency domain. It will beunderstood by those skilled in the art that combined processor 180includes circuitry and/or software to calculate the Fourier transformsand inverse Fourier transforms, or other frequency domain transforms, ofvarious signals, as required.

[0044] Control logic circuitry 176, illustrated in greater detail inFIG. 5, includes voice activity detectors (VAD) 177, double-talkdetector 178, and activity decision logic 179. Control logic 176receives the far-end signal d(t), the estimated echo signal {circumflexover (d)}(t), and the EC signal x(t). Activity decision logic 179receives inputs from the VADs 177 and the double-talk detector 178, anddetermines which speech mode is currently active according toconventional methods. The activity decision logic 179 sends a speechmode indicator to the combined processor 170. This indicator selectivelydefines the mode of operation of the combined processor 170.

[0045]FIG. 6 illustrates an exemplary procedure for implementing thepresent invention. Shortly after a near-end mobile terminal 40establishes a communication link with a far-end conventional telephonehandset 30 (step 200), background noise estimator 182 initializesΦ_(N)(ω) (step 204) and generates Φ_(N+S)(ω)(step 208). Then, averagesignal generator 186 generates (step 210) an average signal {overscore(X)}(ω). The background noise estimator 182 generates (step 220) theestimated noise {circumflex over (N)}(ω) and the average noise{overscore (N)}(ω). If near-end speech is present (step 230), outputsignal generator 184 generates Y(ω) according to Equation 7 (step 260).Further, if neither near-end nor far-end speech is present (step 230,step 240), background noise estimator 182 generates a new Φ^(N)(ω) (step245, optional) and output signal generator 184 generates Y(ω) accordingto Equation 6 (step 260). If near-end speech is not present (step 230)and far-end speech is present (step 240), output signal generatorgenerates Y((ω) according to Equation 6 (step 250). This process (steps208-260) continues until the communication link is disconnected (step270).

[0046] By implementing the integrated residual echo suppression/noisereduction during far-end mode, the present invention eliminates the needfor explicit comfort noise generation by generating an output signalthat is a function of the average signal. Therefore, the far-end usernever experiences the abrupt changes associated with conventional echoprocessing techniques that omit comfort noise.

[0047] The foregoing description and drawings describe and illustratethe present invention in detail. However, the foregoing disclosure onlydescribes some embodiments. Those skilled in the art will understandthat the present invention is not limited to cellular telephones orother wireless communication devices. Therefore, the present inventionembraces all changes and modifications that come within the meaning andequivalency range of the appended claims.

What is claimed is:
 1. A method of reducing residual echo and noise inan echo-containing signal derived from a near-end input signalcomprising: maintaining an average signal comprising an average of anecho-canceled signal across all modes of the near end signal, whereinthe modes comprise a near-end mode, a far-end mode, a double-talk modeand a quiet mode; maintaining an average noise comprising an average ofan estimated noise of the echo-canceled signal across all modes of thenear-end signal, determining a first attenuation factor as a function ofthe average noise; and generating an output signal for transmission to afar-end communication device by applying the first attenuation factor tothe average signal while operating in the far-end mode.
 2. The method ofclaim 1, further comprising determining a second attenuation factor as afunction of the estimated noise and generating the output signal byapplying the second attenuation factor to the echo-canceled signal whileoperating in all modes but the far-end mode.
 3. The method of claim 2,further comprising generating the output signal responsive to one ormore mode indicator signals that indicate whether the far-end mode isactive.
 4. The method of claim 3, further comprising generating the oneor more mode indicator signals responsive to sensing near-end speech andfar-end speech.
 5. The method of claim 1, wherein maintaining theaverage signal comprises maintaining a running average of theecho-canceled signal.
 6. The method of claim 5, wherein maintaining theaverage signal comprises maintaining the running average of theecho-canceled signal according to, {overscore (X)}(ω)=λ{overscore(X)}(ω)+(1−λ)|X(ω)|², where {overscore (X)}(ω) is the average signal,X(ω) is the echo-canceled signal, and λ is an averaging constant.
 7. Themethod of claim 5, wherein maintaining the average signal comprisesmaintaining a weighted average of past samples of the echo-canceledsignals.
 8. The method of claim 1, wherein maintaining the averagesignal comprises maintaining a frequency-domain average value of theecho-canceled signal.
 9. The method of claim 8, wherein maintaining afrequency-domain average value of the echo-canceled signal comprisesmaintaining a running average of weighted spectral magnitudes for theecho-canceled signal.
 10. The method of claim 9, wherein maintaining arunning average of weighted spectral magnitudes comprises filteringsuccessive magnitude samples of the echo-canceled signal with anexponential weighting filter.
 11. The method of claim 10, furthercomprising setting a weighting coefficient of the exponential weightingfilter as a function of speech-frame timing associated with the outputsignal, wherein the exponential weighting filter comprises a firstexponential weighting filter during speech modes and a secondexponential weighting filter during quiet mode.
 12. The method of claim3, wherein maintaining an estimated noise comprises maintaining a firstpower spectral density (PSD) value of the echo-canceled signal for quietmode operation and a second PSD value of the echo-canceled signal acrossall modes of operation.
 13. The method of claim 12, wherein determininga second attenuation factor comprises determining a ratio of the firstPSD value to the second PSD value.
 14. The method of claim 13 whereindetermining the second attenuation factor, β₂(ω), comprises calculatingβ₂(ω) according to,${{\beta_{2}(\omega)} = {1 - \frac{\Phi_{N}(\omega)}{\Phi_{N + S}(\omega)}}},$

wherein Φ_(N)(ω) comprises the first PSD value, and Φ_(N+S)(ω) comprisesthe second PSD value.
 15. The method of claim 12, wherein determining afirst attenuation factor as a function of the average noise comprisesdetermining a ratio of the first PSD value to an average of the secondPSD value.
 16. The method of claim 15, wherein determining the firstattenuation factor, β₁(ω), comprises calculating β₁(ω) according to,${{\beta_{1}(\omega)} = {1 - \frac{\Phi_{N}(\omega)}{{\overset{\_}{\Phi}}_{N + S}(\omega)}}},$

wherein Φ_(N)(ω) comprises the first PSD value, and {overscore(Φ)}_(N+S)(ω) comprises the average of the second PSD value.
 17. Themethod of claim 16, further comprising calculating the average of thesecond PSD value, {overscore (Φ)}_(N+S)(ω), according to {overscore(Φ)}_(N+S)(ω)=λ_(Φ){overscore (Φ)}_(N+S)(ω)+(1−λ_(Φ)Φ) _(N+S)(ω) whereλ_(Φ) is an exponential weighting factor and Φ_(N+S)(ω) is the secondPSD value.
 18. The method of claim 17 wherein the exponential weightingfactor comprises a first exponential weighting filter during speechmodes and a second exponential weighting filter during quiet mode.
 19. Amethod of reducing noise and echo in an echo-containing signalcomprising: receiving a near-end input signal that includes near-endspeech in a near-end mode, echoed far-end speech in a far-end mode, bothnear-end and echoed far-end speech in a double-talk mode, and no speechin a quiet mode; canceling echo from the near-end input signal to forman echo-canceled signal; maintaining an average signal comprising anaverage of the echo-canceled signal across all modes; maintaining anestimated noise for the echo-canceled signal across all modes;generating an average noise comprising an average of the estimatednoise; and generating an output signal for transmission to a far-endcommunication device by applying a first-attenuation factor, determinedfrom the average noise, to the average signal for far-end modeoperation, and applying a second attenuation factor, determined from theestimated noise, to the echo-canceled signal for other than far-end modeoperation.
 20. The method of claim 19, wherein maintaining an averagesignal comprises maintaining a spectral average of the echo-canceledsignal across quiet and speech modes such that the output signalgenerated during far-end mode may be transmitted to the far-endcommunication device without need for added comfort noise.
 21. Themethod of claim 20, wherein maintaining a spectral average of theecho-canceled signal comprises maintaining a running average of spectralmagnitudes obtained from the echo-canceled signal across all modes ofoperation.
 22. The method of claim 19, wherein maintaining an estimatednoise for the echo-canceled signal comprises maintaining a first powerspectral density (PSD) value determined during operation in the quietmode and a second PSD value determined during operation in all modes.23. The method of claim 22, further comprising determining the secondattenuation factor from a ratio of the first PSD value to the second PSDvalue.
 24. The method of claim 22 further comprising determining thefirst attenuation factor from a ratio of the first PSD value to anaverage of the second PSD value.
 25. The method of claim 19, whereingenerating the output signal is based on a spectral subtractionoperation.
 26. An integrated processor for use in a communication deviceto reduce residual echo and noise in an echo-canceled signal derivedfrom a near-end input signal, the processor comprising: an output signalgenerator to generate an output signal for transmission to a far-endcommunication device by applying a first attenuation factor to anaverage signal while operating in a far-end mode, wherein the averagesignal comprises an average of the echo-canceled signal; an averagesignal generator to generate the average signal for use by the outputsignal generator; and a background noise estimator to generate anestimated noise of the echo-canceled signal for use in determining thefirst attenuation factor used by the output signal generator.
 27. Theprocessor of claim 26, wherein the output signal generator is responsiveto one or more mode indicator signals indicating a current mode ofoperation.
 28. The processor of claim 27, wherein said current mode ofoperation includes one of a near-end mode, a double-talk mode, a quietmode, or the far-end mode, and wherein the near-end input signalincludes near-end speech in the near-end mode, echoed far-end speech inthe far-end mode, near-end and echoed far-end speech in the double-talkmode, and no speech in the quiet mode
 29. The processor of claim 28,further comprising decision logic to determine the current mode ofoperation.
 30. The processor of claim 27, wherein the background noiseestimator generates the estimated noise of the echo-canceled signal foruse in determining a second attenuation factor, wherein the outputsignal generator generates the output signal by applying the secondattenuation factor to the echo-canceled signal in all modes other thanthe far-end mode.
 31. The processor of claim 30, wherein the outputsignal generator substitutes average signal for the echo-canceled signaland substitutes the first attenuation factor for the second attenuationfactor during output signal generation responsive to the one or moremode indicator signals indicating that the far-end mode is active. 32.The processor of claim 30, wherein the background noise estimatormaintains the background noise estimate by determining a first powerspectral density (PSD) value of the echo-canceled signal during a quietmode of operation where there is no near-end speech or far-end speechand determining a second PSD value of the echo-canceled signal duringquiet and non-quiet modes of operation.
 33. The processor of claim 32,wherein the background noise estimator determines the second attenuationfactor by determining a ratio of the first PSD value to the second PSDvalue.
 34. The processor of claim 33, wherein the ratio, β₂(ω), of thefirst PSD value to the second PSD value is calculated according to${{\beta_{2}(\omega)} = {1 - \frac{\Phi_{N}(\omega)}{\Phi_{N + S}(\omega)}}},$

wherein Φ_(N)(ω) comprises the first PSD value, and Φ_(N+S)(ω) comprisesthe second PSD value.
 35. The processor of claim 32, wherein thebackground noise estimator determines the first attenuation factor basedon determining a ratio of the first PSD value to an average of thesecond PSD value.
 36. The processor of claim 35, wherein the outputsignal generator calculates the first attenuation factor as a scalingfactor based on the ratio of the first PSD value to the average of thesecond PSD values.
 37. The processor of claim 35, wherein the backgroundnoise estimator determines the first attenuation factor by calculating aratio β₁(ω) according to,${{\beta_{1}(\omega)} = {1 - \frac{\Phi_{N}(\omega)}{{\overset{\_}{\Phi}}_{N + S}(\omega)}}},$

wherein Φ_(N)(ω) comprises the first PSD value, and {overscore(Φ)}_(N+S)(ω) comprises the average of the second PSD value.
 38. Theprocessor of claim 37, wherein the background noise estimator calculatesthe average of the second PSD value {overscore (Φ)}_(N+S)(ω) accordingto, {overscore (Φ)}_(N+S)(ω)=λ_(Φ){overscore(Φ)}_(N+S)(ω)+(1−λ_(Φ))Φ_(N+S)(ω), wherein λ_(Φ) is an exponentialweighting factor, and further wherein the exponential weighting factorcomprises a first exponential weighting filter during speech modes and asecond exponential weighting filter during quiet mode.
 39. The processorof claim 26, wherein the average signal generator maintains the averagesignal as a running average of the echo-canceled signal.
 40. Theprocessor of claim 39, wherein the average signal generator calculatesthe running average of the echo-canceled signal as a weighted average ofpast samples of the echo-canceled signals.
 41. The processor of claim39, wherein the average signal generator calculates the running averageof the echo-canceled signal according to, {overscore (X)}(ω)=λ{overscore(X)}(ω)+(1−λ)|X(ω)|², where {overscore (X)}(ω) is a frequency-domainrepresentation of the running average of the echo-canceled signal X(ω)and λ is an averaging constant.
 42. The processor of claim 26, whereinthe average signal generator maintains the average signal as afrequency-domain average value of the echo-canceled signal.
 43. Theprocessor of claim 42, wherein the average signal generator maintainsthe frequency-domain average value of the echo-canceled signal as arunning average of weighted spectral magnitudes for the echo-canceledsignal.
 44. The processor of claim 43, wherein the average signalgenerator calculates the average of weighted spectral magnitudes byfiltering successive magnitude samples of the echo-canceled signal withan exponential weighting filter.
 45. The processor of claim 44, whereinthe average signal generator sets a weighting coefficient of theexponential weighting filter as a function of speech-frame timingassociated with the output signal, and wherein the exponential weightingfilter comprises a first exponential weighting filter during speechmodes and a second exponential weighting filter during quiet mode. 46.The processor of claim 26, wherein the processor comprises a digitallogic circuit incorporated into a wireless communication device.
 47. Awireless communications device comprising: a receiver for receiving anda far-end signal; a microphone for receiving a near-end signal, whereinsaid near-end signal includes a near-end background noise signal and anecho of said far-end signal; a front-end echo suppressor for generatingan echo-canceled signal as a function of said near-end signal, whereinsaid echo-canceled signal includes a residual echo signal and saidnear-end background noise signal; an integrated processor for reducingresidual echo and noise in said echo-canceled signal comprising: anoutput signal generator to generate an output signal for processing andtransmission to a far-end communications device by applying a firstattenuation factor to an average signal while operating in a far-endmode, wherein the average signal comprises an average of theecho-canceled signal; an average signal generator to generate theaverage signal for use by the output signal generator; and a backgroundnoise estimator to generate an average noise for use in determining thefirst attenuation factor used by the output signal generator, whereinthe average noise comprises an average of an estimated noise of theecho-canceled signal.
 48. The wireless communications device of claim47, wherein the output signal generator is responsive to one or moremode indicator signals indicating a current mode of operation.
 49. Thewireless communications device of claim 48, wherein said current mode ofoperation includes one of a near-end mode, a double-talk mode, a quietmode, or the far-end mode, and wherein the near-end input signalincludes near-end speech in the near-end mode, echoed far-end speech inthe far-end mode, near-end and echoed far-end speech in the double-talkmode, and no speech in the quiet mode
 50. The wireless communicationsdevice of claim 49, further comprising decision logic to determine thecurrent mode of operation.
 51. The wireless communications device ofclaim 49, wherein the background noise estimator generates the estimatednoise of the echo-canceled signal for use in determining the secondattenuation factor, and the output signal generator generates the outputsignal by applying the second attenuation factor to the echo-canceledsignal in all modes other than the far-end mode.
 52. The wirelesscommunications device of claim 51, wherein the output signal generatorsubstitutes the average signal for the echo-canceled signal andsubstitutes the first attenuation factor for the second attenuationfactor during output signal generation responsive to the one or moremode indicator signals indicating that the far-end mode is active. 53.The wireless communications device of claim 51 wherein the backgroundnoise estimator maintains the estimated noise by determining a firstpower spectral density (PSD) value of the echo-canceled signal during aquiet mode of operation where there is no near-end speech or far-endspeech and determining a second PSD value of the echo-canceled signalduring quiet and non-quiet modes of operation.
 54. The processor ofclaim 53, wherein the background noise estimator determines the secondattenuation factor by determining a ratio of the first PSD value to thesecond PSD value.
 55. The processor of claim 54, wherein the secondattenuation factor, β₂ (ω), is calculated according to${{\beta_{2}(\omega)} = {1 - \frac{\Phi_{N}(\omega)}{\Phi_{N + S}(\omega)}}},$

wherein Φ_(N)(ω) comprises the first PSD value, and Φ_(N+S)(ω) comprisesthe second PSD value.
 56. The wireless communications device of claim53, wherein the background noise estimator determines the firstattenuation factor based on determining a ratio of the first PSD valueto an average of the second PSD value.
 57. The wireless communicationsdevice of claim 56, wherein the background noise estimator calculatesthe first attenuation factor as a scaling factor based on the ratio ofthe first PSD value to the average of the second PSD value.
 58. Thewireless communications device of claim 56, wherein the firstattenuation factor, β₁(ω), is calculated according to${{\beta_{1}(\omega)} = {1 - \frac{\Phi_{N}(\omega)}{{\overset{\_}{\Phi}}_{N + S}(\omega)}}},$

wherein Φ_(N)(ω) comprises the first PSD value, and {overscore(Φ)}_(N+S)(ω) comprises the average of the second PSD value.
 59. Thewireless communications device of claim 47, wherein the average signalgenerator maintains the average signal as a running average of theecho-canceled signal.
 60. The wireless communications device of claim59, wherein the average signal generator calculates the running averageof the echo-canceled signal as a weighted average of past samples of theecho-canceled signals.
 61. The wireless communications device of claim59, wherein the average signal generator calculates the running averageof the echo-canceled signal according to, {overscore (X)}(ω)=λ{overscore(X)}(ω)+(1−λ)|X(ω)|², where {overscore (X)}(ω) is a frequency-domainrepresentation of the running average of the echo-canceled signal X(ω)and λ is an averaging constant.
 62. The wireless communications deviceof claim 47, wherein the average signal generator maintains the averagesignal as a frequency-domain average value of the echo-canceled signal.63. The wireless communications device of claim 62, wherein the averagesignal generator maintains the frequency-domain average value of theecho-canceled signal as a running average of weighted spectralmagnitudes for the echo-canceled signal.
 64. The wireless communicationsdevice of claim 63, wherein the average signal generator calculates theaverage of weighted spectral magnitudes by filtering successivemagnitude samples of the echo-canceled signal with an exponentialweighting filter.
 65. The wireless communications device of claim 64,wherein the average signal generator sets a weighting coefficient of theexponential weighting filter as a function of speech-frame timingassociated with the output signal, and wherein the exponential weightingfilter comprises a first exponential weighting filter during speechmodes and a second exponential weighting filter during quiet mode.